CN1685655B - Device and method for detecting useful signals by detecting periodic signals - Google Patents

Abstract

A device for identifying a useful signal by detecting a periodic signal contained in the useful signal comprises a correlation unit (24) for correlating the signal with the sign of the signal while taking a time delay into consideration. The inventive device also comprises an amplitude estimation unit (21) for estimating the amplitude of the signal and comprises a decision unit (14), which is connected down from the amplitude estimation unit (21) and from the correlation unit (24), in order to decide whether the periodic signal is present.

Description

Device and method for detecting useful signals by detecting periodic signals

technical field

The present invention relates to an apparatus and a method for detecting a useful signal by detecting a periodic signal contained in the useful signal.

Background technique

So far, data transfer rates up to 54M bits per second have been achieved in WLANs. Such specifications can be found in "IEEE 802.11a part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed physical Layer in the 5GHZ band" and in "IEEE 802.11b part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Further HighSpeed physical Layer Extension in the 2.4GHz Band" or in "ETSI TS 1-1 761-1 Broadband Radio Access Network (BRAN); Hiperlan Type 2: Physical (PHY)Layer" found in. In order to detect a useful signal, it is necessary to find a periodic signal transmitted at the beginning of a data burst of the useful signal.

FIG. 1 shows a timing diagram in which a periodic signal u(t) with a defined period begins at a specific time to and simultaneously a noise signal n(t). Along the x-axis of the figure is the unit time of a sampling period, that is, the sampling index, and along the y-axis is drawn all the signals including the noise signal n(t) and the periodic signal u(t) The amplitude of the signal r(t). The occurrence of the periodic signal u(t) superimposed on the noise signal n(t) must be detected by a signal detector. If the signal detector described is operating correctly, the periodic signal u(t) must not be found at time t ₀ . However, the possibility of a false detection of the periodic signal u(t) must be avoided as much as possible during this period. On the other hand, once the periodic signal u(t) occurs at time t ₀ , the signal detector must verify the presence of the periodic signal as quickly as possible. Such error rates should also be as low as possible. The periodic signal u(t), and thus the useful signal, should be verified with a probability of 90% within, for example, 4 μs.

Figure 2 shows a possible application of such a signal detector. The analog composite signal r(t) containing the noise signal n(t) and possibly the periodic signal u(t) is amplified by an amplifier with automatic gain control 1 and supplied to an analog/digital converter 2 . And the composite digital signal s(t) collected from the output of the analog/digital converter 2 is supplied to the signal detector 3 . Besides, said signal s(t) is supplied to a receiver 4 . The signal detector 3 informs the receiver whether a periodic signal is detected by a signal appearing at the detector output DA.

Since the described amplifier with automatic gain control (AGC) 1 changes the total power, monitoring only the power change of the signal s(t) cannot be used to detect the periodic signal u(t). An amplifier with automatic gain control 1 enables the signal gain to be adapted as needed from one time to another. For this purpose, the power fluctuates at the input of the analog/digital converter 2 and thus also at the input DE of the signal detector 3, which is why at the input the signal s(t) The power variation of can not provide reliable information to verify the presence or absence of the periodic signal u(t).

FIG. 3 shows the burst structure defined in the aforementioned IEEE specification for data transfer and for synchronization between a transmitter and a sender. The burst structure starts with a preamble STP developed from a short training sequence, and the preamble STP is also called a PLCP preamble or an OFDM training structure. A 0.8 μs long signal (short training sequence), called t ₁ in Figure 3, is repeated 10 times within the STP for a total of 8 μs. In Fig. 3, these repetitions are indicated by _t2 , _t3 , _t4 , ..., _t10 . Immediately behind is a preamble LTP developed by a guard interval (Guard Interval, GI2) and two training sequences T1 and T2. LTP is also extended over the entire 8 μs time. Because the LTP and the burst segment signals immediately after the LTP, Data 1 and Data 2, are not important in this case, they will not be further described in detail in the following articles. A detailed description of this can be found in section 17.3 of the aforementioned IEEE 802.11a specification.

To detect a burst at the receiver terminal, the periodic signals t ₁ , t ₂ , t ₃ , . . . , t ₁₀ of the preamble STP are used. To detect periodic signals in the signal s(t), the similarity of said periodic signals t ₁ , t ₂ , t ₃ , . . . , t ₁₀ to itself during a shift according to the signal period can be used. In the absence of a periodic signal, the signal s(t) should also not exhibit any periodicity.

In the aforementioned second background document ETSI specification, the definition of the training sequence is slightly different, but the periodicity of the periodic signal can also be expressed here. Please refer to Sections 5.7 and 5.8 for references here. For this reason, periodic signals superimposed on noise signals can also be detected in the same way in the case of this specification.

Figure 4 shows the real part 4.1 and the imaginary part 4.2 of the sum of four signals _t1 to _t4 represented in the form of a time course diagram, where the sampling indices are arranged along the x-axis and an arbitrary unit of amplitude is along the y-axis. The sampling rate in the figure is 20 MHz, that is, 16 sampling points correspond to one repetition period (0.8 μs) of the periodic signal u(t). In FIG. 4 , the four signals t ₁ to t ₄ of the periodic signal u(t) should be detectable by the signal detector 3 .

From the prior art "VLSI Implementation of IEEE 802.11a PhysicalLayer, L.Scwoerer, H.Wirz, Nokia Research Center, ^6th International OFDM Workshop 2001-Hamburg, pages 28-1 to 28-4", a signal detector is known as Periodic signals are detected using the following autocorrect functions:

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, τ is a cycle of the periodic signal u(t), and T is the integration or summing cycle. The period τ may be the aforementioned repetition period (0.8 μs) or a multiple thereof, that is, τ=0.8 μs or 1.6 μs or 2.4 μs, etc.

Figure 5 shows two time histories, where in each case the sampling index is arranged along the x-axis and the amplitude is arranged along the y-axis. The upper icon represents the composite digital signal s(t). At sampling index 20, a periodic signal u(t) occurs. And in the lower diagram, the automatic correction function c ₁ (t) in equation (1) as described above is represented in the figure. The signal s(t) does not contain a noise signal in this case. The integration or totalization period T is 0.8 μs. After 1.6 μs (corresponding to 32 sampling points), the last 0.8 μs of the signal s(t) correlates perfectly with the first 0.8 μs of the signal s(t), and after the periodic signal occurs, the The sum of the automatic corrections described above remains unchanged at 1.6 μs.

FIG. 6 also shows two timing diagrams, the upper timing diagram likewise showing the signal s(t), and the lower timing diagram likewise showing the automatic correction function c ₁ (t). The sampling frequency is also maintained at 20 MHz but the signal s(t) described here exhibits a noise component. Here the automatic correction function c ₁ (t) is no longer stable. In addition, the auto-correction function c ₁ (t) also starts to deviate from the value 0, even before the occurrence of the periodic signal. In order to reliably detect said periodic signals, a threshold value has to be taken into account. If the auto-calibration function c ₁ (t) exceeds the threshold value, then it is assumed that the periodic signal is present. The higher said threshold value, the lower the probability that a periodic signal is erroneously detected by the automatic correction according to the function c ₁ (t) described above. However, the result of using such a high threshold tends to take a lot of time before the periodic signal is detected.

The automatic correction c ₁ (t) is also related to the power of the signal s(t). Therefore, said threshold must match said signal power. The average value of the power of the signal s(t) is not constant because the variable gain amplifier 1 is arranged upstream of the signal detector 3 in an attempt to maintain the output signal within a range. And it is necessary to do so in order to avoid overloading of the analog/digital converter 2 . And even if the input signal r(t) as shown in FIG. 2 exhibits a constant average power, it is impossible to set the variable gain amplifier to the corrected value immediately. First it needs to go through a series of adjustments. Due to the variation of the gain, in any case there must be fluctuations in the average power of the signal s(t) at the input of said signal detector 3 . To this is added that when the periodic signal is detected and the useful signal is received, the variable gain amplifier 1 is normally only set to a fixed final value. For this reason, the power has to be estimated during the detection. In the prior art, the following equation is used to estimate the power of the signal s(t):

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Said power p(t) is detected over the last T seconds of the signal s(t) used during automatic calibration. During this process, it must be noted that the self-correcting delayed signal s(t-τ) does not exactly refer to its power, as shown in equation (2). For this reason, a change in the amplifier gain that cannot be detected immediately is determined entirely by adjusting the threshold.

A better approach to this part is to estimate the signal components (including the signal s(t) and the delayed signal s(t-τ) together, multiply them with each other, and then solve for this The power of the root of the product). However, this would disadvantageously result in a significantly more expensive implementation method.

The determination of whether the periodic signal occurs is determined by the following conditions:

c ₁ (t)≥p(t)*thr (3)

Wherein, thr represents the threshold value of automatic correction (not limited by power). If the c ₁ (t) is greater than or equal to the product of the power and the threshold value thr, it is the assumption that a periodic signal appears.

The magnitude of the threshold thr is a compromise between wanting a high reliability of periodic signal detection and, on the other hand, the fastest possible detection of periodic signals.

The block diagram shown in FIG. 7 represents the configuration of a signal detector 3 for implementing the equations embodied in the prior art described above. Wherein thick lines represent complex signals and thin lines represent real signals.

The signal detector 3, as shown in the block diagram of FIG. Said input signal s(t) is supplied to a unit for power estimation 13 to provide at its output said power estimation signal p(t) calculated according to equation (2). For this purpose, the unit 13 for power estimation has a unit for squaring a quantity 5 and a comparison adder 6 . At the same time, said signal s(t) is supplied to an automatic correlation unit 15 . The auto-correlation unit 15 includes a unit 9 for forming a conjugated complex signal, a delay unit for delaying the signal s(t) by the period τ, and a multiplier 16 for To multiply the signal s(t) by the delayed complex conjugate signal s*(t-τ). An analog adder 11 with an incrementing period T and a unit 12 for generating an absolute value are provided after said multiplier 16 . The output of the auto-correlation unit 15 is connected to a first input of a decision unit 14 . At a second input of the decision unit 14, the thr appears. A third input of the decision unit 14 is connected to the unit 13 for power estimation. The threshold value thr is adjusted by the multiplier 7 . The threshold value according to equation (3) is checked via a comparator 8 . At the output DA of the signal detector 3, a detector signal d(t) can be obtained to clearly indicate whether a periodic signal is detected or not.

It is an object of the present invention to specify an apparatus and a method for detecting a periodic signal, and to detect a periodic signal reliably and quickly with the smallest possible execution budget. In particular, variations in the strength of the input signal do not significantly affect the reliability of detection.

Contents of the invention

The object of the present invention is achieved by a device for detecting a periodic signal and by a method having the features described in this application.

The device according to the present invention for detecting a useful signal by detecting a periodic signal included in said useful signal has a correlating unit for correcting a signal, which may include a periodic signal, by The sign of the signal corrects the signal by taking into account a time delay between the signal and the sign of the signal. In addition, the device further includes an amplitude estimation unit for estimating the amplitude of the signal. Finally, a determination unit for determining whether the periodic signal is present is connected downstream of the amplitude estimation unit and the correlation unit.

The device for detecting a useful signal by detecting a periodic signal contained in said useful signal according to the present invention presents the following steps. A signal, possibly including a periodic signal, is corrected with the sign of said signal taking into account a time delay. Estimate the amplitude of the signal. Whether the periodic signal appears is determined by the amplitude and the signal obtained during the calibration.

Advantageous developments of the present invention can be obtained from the technical features specified in the detailed description.

According to the device of the present invention, said correlating unit may present a unit for determining said symbol and delaying said signal. In addition, the device preferably further includes a multiplier, a first input of the multiplier is connected to the unit for determining the sign and delaying the signal, and A second input of the multiplier is used to receive the signal. A first summing unit is connected downstream of the multiplier.

In an embodiment of the present invention, the amplitude estimation unit presents a unit for forming the absolute value of the real part and the absolute value of the imaginary part of the signal, and a second summing unit is connected downstream.

In another specific embodiment of the present invention, said decision unit presents a multiplier for multiplying a signal output by said amplitude estimation unit by a predetermined value, and a comparator for comparing The signal output by the correlation unit and the signal output by the multiplier.

In another embodiment of the present invention, a unit for generating absolute values is provided and connected downstream of said first summing unit.

In another embodiment of the invention, said means for generating the absolute value presents a second decision unit for the purpose of estimating the absolute value. The second determination unit is configured to estimate the absolute value of the signal supplied by the first summing unit by means of an evaluation function defined piecewise.

According to the device of the present invention, a unit for separating signals may be provided upstream connected to said second decision unit.

According to the method of the present invention, the signal and the sign of the signal can be obtained by multiplying the signal and the time-delayed signs of the signal and possibly conjugate complex numbers with each other and summing results to correct.

In a preferred embodiment of the method of the present invention, said amplitude is multiplied by a predetermined value and then compared with said absolute value to determine whether said periodic signal is present.

The device and method according to the present invention can preferably be used in a wireless local area network, especially a wireless local area network according to IEEE 802.11a standard or IEEE 802.11g standard or ETSI TS 101761-1 (BRAN), Hiperlan type 2 standard

Description of drawings

In the following description, the present invention will be described in detail by means of specific embodiments and with the attached icons, wherein these attached icons are briefly described as follows:

Figure 1 shows a time course diagram of a noise signal to be evaluated, wherein a periodic signal is superimposed on said time course diagram;

Figure 2 shows a block diagram of a possible application of a signal detector for detecting periodic signals;

Figure 3 shows a burst structure as described in the IEEE specification;

FIG. 4 shows a timing diagram of signals during the transmission of the training rate sequence preamble as described in FIG. 3;

Fig. 5 shows the signal variation of a signal present at the input of the signal detector and the associated variation of said automatic correction function;

Fig. 6 shows the signal variation of a signal presenting a noise component and present at the input of the signal detector and the associated variation of the automatic correction function;

FIG. 7 shows a block diagram comparing the structure of a signal detector in the prior art;

Figure 8 shows a block diagram of the configuration of a signal detector according to the present invention; and

FIG. 9 shows a configuration diagram of a unit for generating absolute values used in the embodiment shown in FIG. 8 .

Detailed ways

The descriptions of FIG. 1 to FIG. 7 will not be discussed in detail in the following description, but the technical features related to the present invention in the relevant references will be used as the detailed description as described above.

According to the signal detector of the present invention, as shown in FIG. 8, it has an input DE, where an input signal s(t) can be applied, that is, it can be the complex digital output of the analog/digital converter 2 Signal. Said input signal s(t) is supplied to a unit 21 for estimating the amplitude such that said unit 21 supplies at its output a signal having an average amplitude value m(t). At the same time, the signal s(t) is supplied to a correlation unit 24 , and the output of the correlation unit 24 is connected to a first input of a decision unit 14 . Furthermore, a second input of the decision unit 14 presents a threshold value thr. A third input of the decision unit 14 is connected to the unit 21 for estimating the amplitude. A detection signal d(t) can be obtained at the output DA of the signal detector to specifically indicate whether a periodic signal is detected.

The correlation unit 24 includes a unit 17 for determining a sign, and the unit 17 for determining a sign simultaneously performs complex conjugate of the determined sign value. After the symbol-determining unit 17 is a delay unit 10, and the delay unit 10 is used to delay the signal s(t) for a period τ. A multiplier 16 multiplies the delayed symbol value output by the delay unit 10 by the signal s(t). After said multiplier, there is an analog adder 11 with an incrementing period T and a unit 19 for generating absolute values.

A thick line in the diagram indicates a complex signal (two real number signals), a thick dotted line indicates a complex 2-bit signal (two real number 1-bit signals), and a thin line indicates a real number signal.

To calculate said correction function c(t), said correlation unit 24 uses the following formula:

$\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sgn</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

or the formula:

$\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sgn</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

From a mathematical point of view, formula (4) and formula (5) can lead to the same result, because whether the first conjugate complex part is formed is determined by the sign described later, or whether the first signal is determined by It is immaterial whether or not the conjugated complex moieties described later are formed. However, in practice, formula (5) is executed, more specifically, formula (5) is executed during the implementation process on a VLSI (very large scale integration) chip, that is, the conjugate complex number occurs after the symbolic calculation, will be more effective.

Unlike the prior art, the sign of the input signal s(t) is taken into account in the automatic correction calculation of the present invention.

The sign of the complex signal s(t) consists of the following formula:

sgn(x)＝sgn(Re(x))+j sgn(Im(x)) (6)

Among them, j represents the imaginary part unit. Calculating the automatic correction function c(t) by one of the aforementioned formula (4) or formula (5) results in the following advantages.

The result of the automatic correction is independent of the amplitude of the delayed signal component (and thus also independent of the adjustment of the amplifier 1 ). The symbols in question have a fixed average amplitude value equal to one. The result of the automatic calibration described is therefore less strongly influenced by the gain setting at amplifier 1 .

Another advantage resides in the significant reduction in the number of complex multiplication operations required to compute decisions. The complex multiplication represents the multiplication of complex signals. In FIG. 8 , how the calculations are simplified is shown by the style of the lines. The multiplication operation described requires a simple multiplier 16 in the form of a controlled adder or subtractor. A third advantage is that fewer storage devices are required to store the delayed portion of the input signal s(t). Each signal sample only needs two bits of storage space to store the sign of the signal s(t).

Since one of the two signals has a known fixed amplitude, the mean amplitude value m(t) rather than the power value of the signal s(t) is used to set the The threshold value thr. The mean amplitude value m(t) can be calculated, for example, by solving the square root of the estimated power value p(t) determined by equation (2).

However, in order to simplify the calculation of the amplitude value m(t) by means of the unit 21 for estimating the amplitude, the following advantageous equations can also be used:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Re</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Im</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In equation (7), all multiplicative expressions can be avoided, thus, on the calculations performed numerically in said equation (calculating the absolute values of the real and imaginary parts by the unit 20 forming the absolute value, and by By performing the addition of two absolute values by the comparison adder 6), the chip area on a VLSI chip, as well as the power consumption can be reduced. The summation at the analog adder can be extended, for example, over 16 time indices to correspond to a sampling time of T = 0.8 μs with a sampling rate of 20 MHz.

On the basis of the estimated auto-correction c(t), the estimated amplitude m(t) and the fixed threshold value thr (a judgment criterion that will be further specified in the following specification) provide the periodic signal Is there any information present.

The criteria for judging are:

c(t)≥m(t)*thr (8)

If the condition of the inequality (8) is satisfied, it is assumed that the periodic signal occurs. If not, it is assumed that the periodic signal has not occurred.

The signal detector 3 can be simplified by performing the absolute value generated from the amplitude during the calculation of equation (4) or equation (5) by the autocorrelation unit 24 . Normally, this requires multiplication and square roots. This situation can be avoided by defining a function of the amplitude estimation segment by segment. Therefore, said amplitude is estimated by the following equation:

The function defined piecewise according to equation (9) can also be used to solve equation (7). In this case, the unit 19 for estimating the absolute value must be used instead of the unit 20 for generating the absolute value.

FIG. 9 shows a block diagram for the unit 19 used to estimate the absolute value. As shown in FIG. 8, the unit 19 for estimating the absolute value has a unit 22 for separating the added signal cn(t) into a real part and an imaginary part. In addition, if the imaginary part is less than 1/4 of the real part, the output of the logic circuit 23 presents the absolute value of the real part. In contrast, if the real part is less than 1/4 of the imaginary part, the output of the logic circuit 23 presents the absolute value of the imaginary part. If it is other than the above two conditions, the value of 3/4 of the sum of the absolute value of the real part and the absolute value of the imaginary part will appear at the output of the logic circuit 23 .

As can be seen from FIGS. 8 and 9, the separation from the real part multiplier 7 does not require an additional multiplier (because the previously mentioned multiplier 16 can be used to estimate all The aforementioned mean amplitude value m(t) and a multiplier for estimating the aforementioned absolute value via unit 19 may be completely omitted). Due to these simplifications and the reduction of memory cells, significant chip area savings and significant power consumption reductions can be clearly compared with the signal detector shown in FIG. 7 .

Naturally, the specific embodiment of the present invention shown in FIG. 8 can also be used in the circuit of FIG. 2 . Apart from this, according to the two aforementioned specifications, the invention is not limited to the detection of periodic signals. In particular, the invention can also be used to detect actual signals.

Description of component symbols

1 amplifier with automatic gain control

2 Analog/Digital Converter

3 signal detector

4 receivers

5 Square operation unit 6 Addition operation unit

7 Multiplication operation unit 8 Comparison operation unit

9 Conjugate operation unit 10 Delay operation unit

11 Addition operation unit 12 Absolute value operation unit

13 Power estimation unit 14 Decision unit

15 Correlation unit 16 Multiplication unit

17 Symbol operation unit 19 Absolute value operation unit

20 Absolute value calculation unit 21 Amplitude estimation unit

22 Separate the real part and imaginary part unit 23 Logic circuit

24 related units

Claims (15)

1. one kind is included in one-period signal and detect the device of described useful signal in the useful signal by detection, comprises:

One correlation unit (24), with so that may contain a signal s (t) of described periodic signal and be associated with a signal sgn (s (t-τ)), wherein said signal sgn (s (t-τ)) is the symbol of the described signal s (t-τ) that postponed,

One amplitude evaluation unit (21), in order to estimating the amplitude of described signal s (t), and

One decision unit (14) is connected to the downstream of described amplitude evaluation unit (21) and described correlation unit (24), in order to by relatively judging the existence of described periodic signal.

2. device as claimed in claim 1 is characterized in that described correlation unit (24) comprises:

Unit one (17,10), in order to determining described symbol and to postpone described signal s (t),

One multiplier (16), wherein

First input of described multiplier (16) is connected to the downstream of described unit (17,10), with deciding described symbol and be used for postponing described signal s (t), and

Second input of described multiplier receives described signal s (t), and

One first adds up unit (11), is connected in the downstream of described multiplier.

3. device as claimed in claim 2, it is characterized in that described amplitude evaluation unit (21) comprises a unit (20) in order to the absolute value of the absolute value of the real part that forms described signal s (t) and imaginary part, and one second add up unit (6), be connected to described in order to the real part that forms described signal s (t) absolute value and the downstream of the unit (20) of the absolute value of imaginary part.

4. device as claimed in claim 1, wherein said decision unit (14) comprises:

One multiplier (7), in order to a predetermined value on the signal times that will be exported by described amplitude evaluation unit (21), and

One comparator (8) is in order to compare signal of being exported by described correlation unit (24) and the signal of being exported by multiplier (7).

5. device as claimed in claim 3 is characterized in that described correlation unit (24) also comprises the unit (19) that has in order to the generation absolute value, and it is connected in the downstream of the described first totalling unit (11).

6. device as claimed in claim 5, it is characterized in that in described amplitude evaluation unit (21) and in order to the described unit (20) that forms absolute value with and/or be connected in described first and add up the downstream of unit (11) and be to comprise one second decision unit (23) for the purpose of estimating absolute value in order to the described unit (19) that produces absolute value, the described second decision unit (23) is construed as to estimate the absolute value of a suppling signal by the mode of an evaluation function of definition piecemeal.

7. device as claimed in claim 6 is characterized in that in order to a separation signal unit (22) that described suppling signal is separated into real part and imaginary part be the upstream that is connected the described second decision unit (23).

8. arbitrary described device that relates to as claim 1-7, be applied in the WLAN, wherein said WLAN is according to IEEE 802.11a standard or IEEE 802.11g standard or ETSI TS 101 761-1 (BRAN), the WLAN of Hiperlan type2 standard.

One kind by detection be included in the useful signal one-period signal to detect the method for described useful signal, it is characterized in that:

The one signal s (t) that may contain described periodic signal is associated with the delayed symbol of described signal s (t),

Estimate the amplitude m (t) of described signal s (t),

By described amplitude m (t) and during be associated the resulting signal in back make a judgement, whether exist to differentiate described periodic signal.

10. method as claimed in claim 9, it is characterized in that by described signal s (t) is multiplied each other each other with the multiple conjugate value of the delayed symbol of described signal s (t) and with one via the resulting consequential signal addition that is associated, described signal s (t) is associated with the delayed symbol of described signal s (t).

11. method as claimed in claim 10 is characterized in that from by forming an absolute value c (t) the resultant signal cn of addition (t).

12. method as claimed in claim 11 is characterized in that utilizing an evaluation function of definition piecemeal to estimate described absolute value c (t).

13. method as claimed in claim 11 is characterized in that described amplitude m (t) is multiplied by a predetermined value, and is comparing to judge whether described periodic signal exists with described absolute value c (t) subsequently.

14., it is characterized in that described useful signal has signal for useful in a WLAN as the arbitrary described method of claim 9-13.

15. method as claimed in claim 14, it is characterized in that described WLAN is according to IEEE 802.11a standard or IEEE 802.11g standard or ETSI TS 101761-1 (BRAN), the WLAN of Hiperlan type 2 standards.

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